Modern carburetors normally include fuel bowls that serve as local reservoirs for fuel that is supplied into the barrels of the carburetor and ultimately into the cylinders of a combustion engine. Typically, fuel bowls comprise an inner fuel cavity in which fuel is held, one or more inlet ports that receive fuel from the vehicle's fuel system, a fuel valve that opens and closes to control supply of fuel from the inlet port into the fuel cavity, and a float mechanism that regulates opening and closing of the fuel valve.
Before passing into the barrels of the carburetor, the fuel usually first flows through a fuel metering block which pre-emulsifies the fuel for later atomization within the carburetor barrels. In order for the metering blocks to function properly, the fuel held within the fuel bowl must be between certain predetermined levels. When the level of fuel within the fuel bowl is too low, the metering jets of the metering blocks are not supplied with fuel, resulting in inadequate supply of fuel to the carburetor barrels. On the other hand, when the level of fuel is too high within the fuel bowl, too much fuel can be delivered into the carburetor, resulting in inadequate combustion of the fuel within the engine.
Fuel bowls normally are provided with trickle holes that permit the carburetor user or service technician to observe how much fuel is contained within the fuel bowls. These trickle holes typically comprise threaded openings formed in the side of the fuel bowl that are adapted to receive a threaded trickle plug. To determine the level of fuel in the fuel bowls in such systems, the trickle plug is removed. Since the trickle hole is positioned in the fuel bowl such that the bottom edge of the hole is even with the nominal operating level of fuel for the fuel bowl, proper fuel levels are indicated when the fuel barely trickles out of the hole.
Although useful for indicating the amount of fuel in the fuel bowl, trickle holes present many disadvantages to the carburetor user. One problem with trickle holes is that the level of fuel contained within the fuel bowls cannot be determined without first removing the trickle plug with a tool. Another problem is that fuel is spilled when the trickle plug is removed if the fuel level is higher than the bottom edge of the trickle hole. This spillage creates a fire hazard and further creates a mess that should be cleaned up. A further problem with trickle holes relates to accuracy in fuel level measurement. Specifically, the trickling of fuel provides a very imprecise quantification of the amount of fuel contained in the fuel bowl. For instance, if the user wishes to operate the carburetor with relatively high levels of fuel within the fuel bowls, he or she must guess as to the level of fuel that will be contained within the fuel bowl by observing the rate of fuel flowing out from the trickle hole.
In response to the difficulties associated with conventional trickle holes and plugs, sight glasses have been used in place of metal trickle plugs. These sight glasses are made of polycarbonate material such as plexiglass and, like conventional trickle plugs, are provided with outer threads such that the sight glass can be directly threaded into the trickle hole. Although permitting the user to view the level of fuel contained in the fuel bowls without the need of removing a trickle plug, these polycarbonate sight glasses create other problems. In that these sight glasses have polycarbonate threads, they are susceptible to damage from over-torquing. Further, because the positioning of conventional trickle holes is such that the bottom edge of the trickle hole is even with the nominal operating level for the fuel bowl, the fuel level within the fuel bowl is difficult to see. This problem is exacerbated by the fact that discoloration of the sight glass typically occurs after extended use in the fuel bowl. Moreover, polycarbonate sight glasses tend to fail from fatigue when used for extended periods of time.
Accordingly, it can be understood that it would be desirable to have a means of determining the level of fuel within a fuel bowl which permits the user to quickly and easily determine the fuel level without the need for tools and without spillage of fuel. The disclosure of the present invention provides one such means.